Business and consumers use a wide array of wireless devices, including cell phones, wireless local area network (LAN) cards, global positioning system (GPS) devices, electronic organizers equipped with wireless modems, and the like. The increased demand for wireless communication, and other mobile, devices has created a corresponding demand for technical improvements to such devices. Generally speaking, more and more of the components of conventional radio receivers and transmitters are being fabricated in a single integrated circuit package.
One important aspect of wireless communication devices having integrated circuits is battery life. In order to maximize battery life for these wireless communication devices, much emphasis has been placed on minimizing power consumption in the integrated circuits of the wireless communication devices. One of the largest power consumers in a transmitter for a wireless communication device is the power amplifier. Thus, in order to minimize overall power consumption, a reduction in the power consumption of the power amplifier is often attempted.
Conventional approaches to minimizing power consumption in power amplifiers include envelope elimination and restoration (EER). This technique uses a high efficiency, non-linear power amplifier, such as a Class C power amplifier, instead of a low efficiency, linear power amplifier, such as a Class A power amplifier. However, if the power supply for the power amplifier is high frequency, such as 5 MHz or higher, instead of DC or low frequency, EER does not provide a workable solution.
Because many cellular telephone and other advanced signaling systems use higher order modulation with amplitude components in addition to phase components, linear power amplifiers are used in these systems. Thus, EER techniques may not be implemented to improve power amplifier efficiency in these systems. In addition, linear power amplifiers are generally even less efficient that non-linear power amplifiers. Therefore, a linear power amplifier efficiency improvement is needed that provides high bandwidth, in addition to high efficiency.
Discrete components, such as inductors and capacitors, of power amplifiers generally have to handle up to five times the desired tracking frequency for the power amplifier. However, typical discrete components are not specified for more than 1 MHz, and with pulse-width modulation techniques, the components need to handle up to 25 MHz for a 5 MHz tracking bandwidth. Thus, current technology does not provide components with the needed specifications to improve the efficiency of linear power amplifiers using conventional techniques.